Vehicle manufacturing ab initio is no joke. There are so many specialized items. For example fuel injection system, suspension, axle, upholstery, electrics etc are all made by different companies. It would be quite a while before Pakistan is capable of manufacturing any 4x4 motor vehicle from scratch. Even in Europe, engines are made at a different factory and body at a different factory even in a different country.
Economy of scale is also important. It is far more economic to import the vehicle as CKD (complete knock down) condition and assemble the same. HIT is doing a great job converting the basic vehicle into specailized versions.
GP vehicles (that is why it was called a Jeep) for military use have to be especially strong. These are slung underneath a helicopter or dropped with a parachute from C-130 in a hostile environment. The vehicle should be sturdy enough to take such beating and be driven off right away.
Willys Jeep and Land Rover Defender are the only real all purpose military vehicles and these have a very long life. Don’t think PA is wasting money; they have the best vehicle in the world.